1. Field of the Invention
The invention relates to a synchronizing roller arrangement for transporting sheets into a sheet-processing machine and, more particularly, such a synchronizing roller arrangement which is disposed on a cyclically rotating shaft and pressable with adjustable contact pressure against a transport roller.
In the case of a single-sheet feeder, the uppermost sheet of a sheet pile is gripped in a leading-edge region thereof by means of a suction bar, is separated or singled, is lifted between a synchronizing roller and a transport roller, and carried therefrom via a sheet guiding device to the grippers of a cylinder of the sheet-processing machine. The synchronizing roller arrangement is either a roller with a continuous shaft which carries rubber rings at defined spaced intervals thereon, or individual rollers which are rigidly secured to a cyclically rotating shaft. The cycling or clocking itself occurs in such a manner that the synchronizing roller assembly is slipped onto the transport roller, when the sheet is accepted or transferred from the suction bar, and is lifted from the transport roller, the instant that the grippers of the cylinder have gripped the sheet. This latter action means that the sheet can be freely entrained by the grippers.
To assure a problem-free transport of the sheets to the cylinder of the sheet-processing machine, the synchronizing rollers operate at a higher speed than the speed of the printing press. This increased speed is necessary so that the sheets can catch up with the gripper stops and thus be correctly aligned therewith.
For optimal sheet transport, the speed of the suction device and the speed of the transport rollers must be optimally coordinated with or adjusted to one another. Optimal sheet guidance can be attained only if the suction devices can pivot into the operating range of the synchronizing roller during the pivoting motion executed in the sheet feeding direction. If a continuous synchronizing roller is used, this is not possible so that, in such a case, it is impossible to assure optimal adjustment or coordination between the cycling or clocking of the suction devices and of the synchronizing roller.
In a printing press, sheets of different sizes or formats and of different quality are processed. To meet the various demands, it must be possible to set or adjust the synchronizing roller to the transport roller. If individual synchronizing rollers are used instead of a roller with a continuous shaft, a defined axial adjustment of the various synchronizing rollers must be required. Only in this way can the delivery of paper to the sheet-processing machine be attained with the requisite speed and the requisite accuracy.